Foundat'n Pad

Home Up

BEFORE THE ARCHITECTCUSTOM HOME DESIGNING BACKGROUND – HOUSE DESIGN ARTICLES

ALL ABOUT HOUSE FOUNDATION PROBLEMS and YOUR HOME PAD FOOTING DESIGN

By Before The Architect  Copyright 2009

YOU MAY FREELY QUOTE THE AG WITH PROPER ATTRIBUTION

 

Symmetry?   The eye looks for it, the mind's eye expects it, the mind is comforted by it.  It's a designer's habituation.  Reined in this side of obsession, it suits principles if not purposes.  Be not smitten.  It may be likened to the frame around a painting and may be artful; it's not art.  At its best, it counterpoints inspiration, its complement.  At its worst, it’s inspiration’s antonym, a kiss from your sister. Before The Architect

Foundat'n Plan Design Foundat'n Plan Close Foundat'n Plan Closer Anchor Bolts Concrete Design Concrete Joints Drainage Slopes Footing Drain Foundat'n Pad Foundat'n Speak Foundat'n Strip Gas Curb Grade Beam Slab Foundation Masonry Ledge Masonry Wythe Mod'd Grade Beam Pilasters Placement Radon Mitigation Rebar Reinforced Reinforced Corners Scored Concrete Slab-On-Ground Stone Water Table

QUESTION: WHASSUP WITH HOUSE  FOUNDATION PROBLEMS?

ANSWER:  PRETTY NEAR NOTHING WITH A GOOD HOME FOUNDATION PLAN.

SPREAD FOOTING IN A HOME FOUNDATION PLAN

Introduction

bullet This article is about a home foundation spread footing
                  o       Identity

o       Design

o       Construction 
 

Comment:  Before The Architect (BTA) assumes that these spread footings as with all other footings are sited on substrates of reasonable bearing capacity and engineered when needed – a condition that, in BTA’s experience, is very most often readily identifiable even in the design stage, and, if not, then onsite. 
 

Identity

bullet As with most other footings, a spread footing can go by other names, and ‘footer’ can be substituted for ‘footing’
                  o       Concrete pad

o       Footer

o       Footing pad

o       Individual footing

o       Isolated footing

o       Pad

o       Pad footing

o       Post pad

o       Single footing

o       Spot footing

o       Spread footing

o       DIY pad

o       Precast footing

o       Spread beam

 

bullet There are other common, concrete footings, don’t you know?
                  o       T-wall a/k/a strip footing 

o       Grade beam

o       Modified grade beam

o       Turndown footing 

Design

bullet This custom home designer’s experience is that spread footings are less likely of footings to be engineered, closely tied with turndown footings for being made on the fly
                  o       Cheap

o       Easy

o       More often overbuilt at minimal marginal cost increment
 

bullet In BTA’s book, a spread footing
                  o       Shall be on each side not less than twice the width (or diameter) of that which is supported

o       Shall be in most applications

§         Monolithic

§         Regular in all aspects 
 

Spread Footing With Pier, Section in Elevation, Scaled

 

KEY:
ABV=ABoVe; APX=APproXimately; BEL=BELow; BOF=Bottom Of Face; BOT=BOTtom; CONC=CONCrete; CONT=CONTinuous; CVR=CoVeR; D=Depth; DIA=DIAmeter; DIR=DIRection; DN=DowN; EQV=EQuiValent; FDN=FounDatioN; FGL=Finish Grade Level; FSN=FaSteN; FTG=FooTinG; GaLVanized; MIN=MINimum; NGT=Not Greater Than; NLT=Not Less Than; PT=Preservative-Treated; RR=RebaR; SF=Square Feet; SUBS=SUBStrate; T&B=Top & Bottom; TOF=Top Of Face; TYP=TYPical; W=Width; W:C=Water-to-Cement ratio; WL=WaLl
 

o       Shall be reinforced by

§         Not less than 4-Grade 50-#5 rebar in rectilinear pattern

§         With 3/4 linear inch plus maximum aggregate diameter cover and not more than 3 linear inches cover, which can devolve to two layers with a thickened pad

o       Bottom of face shall be not higher than the bottoms of face of new, proximate footings

o       If with pier, or pedestal

§         Then shall not be less than half the width dimension of the spread footing

§         Then shall be reinforced on the vertical with not less than 2-#5 rebar from the footing bottom of face plus 3/4 linear inch plus maximum aggregate size cover to the pier top of face less 3/4 linear inch plus maximum aggregate size cover and in either case not greater than 3 linear inches cover  

 

Comment:  The spread footing in the illustration to follow is notable for at least one indication; namely, it can be envisioned from any orthogonal as the same section. 
 

Comment:  The home design author notes an historical reference; namely, this drawing executed some time ago specifies #4 rebar, a sizing OK in its time (not so long ago); however, these days, BTA specifies not less than #5 in residential applications of reinforcement – deformed generally, smooth or sleeved across contraction, or control, joints exceptionally.  Further, this custom home designer sees such up-sizing more rather than less frequently in home design and home building as time passes.  
 

Foundation Building

bullet Where to design-in a spread footing
                  o       Generally, centered below the load the spread footing bears

o       Specifically, BTA applies spread footings in 3 conditions

§         Below a grade beam

§         Below a modified grade beam

§         Below anywhere else that a point or concentrated load path to earth travels or is otherwise guided to travel  
 

bullet Below a grade beam
                  o       Where exactly below a grade beam is addressed elsewhere hereunder in the Grade Beam subchapter

o       Here’s an example of a spread footing with pedestal, or pier, below a grade beam 
 

Spread Footing Below Grade Beam at Intersection with Modified Grade Beam, Plan View, Scaled 

 

KEY:
ABS=ABSOLUTE; BEL=BELOW; BM=BEAM; BOT=BOTTOM; BOT=BOTTOM; BW=BOTH WAYS; CONT=CONTINUOUS; CVR=COVER; D=DEPTH; FTG=FOOTING; GD=GRADE; HOR=HORIZONTAL; JT=JOINT; LI=LINEAR INCH; NGT=NOT GREATER THAN; NLT=NOT LESS THAN; PRM=PERIMETER; RR=REBAR; SOG=SLAB-ON-GRADE; SPD=SPREAD; T&B=TOP & BOTTOM; TOF=TOP OF FACE; TYP=TYPICAL 
 

bullet Spread footing below a modified grade beam
                  o       As for a spread footing below a modified grade beam, home design and home building guidelines are presented hereunder in the subchapter Modified Grade Beam

o       Here’s an example of a spread footing below a modified grade beam 
 

Spread Footing Below Modified Grade Beam Intersections, Plan View, Scaled

KEY: 
BOF=BOTTOM OF FACE; CL=CENTERLINE; CONT=CONTINUOUS; CVR=COVER FTG=FOOTING; GBM=GRADE BEAM; INT=INTERIOR; LI=LINER INCH; MIN=MINIMUM; NLT=NOT LESS THAN; OC=ON CENTER; RR=REBAR; SIM=SIMILAR; SOF=SIDE OF FACE; SOG=SLAB-ON-GRADE; SPD=SPREAD; TYP=TYPICAL 
 

bullet Spread footing anywhere else that a point or concentrated load path to earth travels or is otherwise guided to travel
                  o       There can be several conditions in a home design that are ripe for spot footings, including but not limited to –

§         Generally, load paths

ü      interiors to perimeters or otherwise

ü      Not to t-wall interiors

§         Specifically among others –

ü      Feet of a pool table

ü      Interior, bearing columns

ü      Exterior, bearing columns

ü      Pedestals to certain fireplaces, e.g., Rumfords  
 

bullet Here’s an example of an interior bearing column supported by a spread footing
                  o       A column to-be will be below the terminus of an engineered beam done by others in a wing wall at the foundation inflection

o       Which beam is double-decked, that is, set atop another such wing wall on L0 and L1 to distinguish entrance to important space on each level  
 

Spread Footing Below Interior Bearing, Plan View, Scaled

 

KEY:
AB=ANCHOR BOLT; ABS=ABSOLUTE; BEL=BELOW; BM=BEAM; BOT=BOTTOM; BW=BOTH WAYS; CONT=CONTINUOUS; D=DEPTH; EL=ELEVATION; FTG=FOOTING; GD=GRADE; GRD=GRADE; HOR=HORIZONTAL; JT=JOINT; LI=LINEAR INCH; NLT=NOT LESS THAN; PNL=PANEL; PRM=PERIMETER; PSG=PASSAGE; RR=REBAR; SOG=SLAB-ON-GRADE; SPD=SPREAD; TOF=TOP OF FACE; TYP=TYPICAL 
 

bullet Of note –
                  o       Panel and passage are

§         Referenced to indicate places where anchor bolts shall not be set and for which compensation shall be made (dimensions that site these features are herewith omitted for clarity of expression)

§         Mullioned consonant with respectful observation of Traditional Style befitting this particular exterior (and a common sense approach to framing)

o       Changes in elevation respect the reality of a walk-out, covered deck 6 linear inches below the habitable interior

o       The control, or contraction, joint in the grade beam is off-center, forced so by a need to square-up the joint at its terminus with the wall and still centrally bear critical path loads from the roof, three ceilings and two floor systems

o       This spread footing is not square in plan view, but rather rectangular – some would call it irregular – because this designer’s not entirely sure where in the wing walls will an engineer set the columns either side of a broadly opened portal or even whether more than one column will be applied to either side, since this designer indicated on the L0 and L1 floor plans that more than one column thereabouts would be in-style  
 

Comment:  While not specified herewith, the custom home designer expects, that in gauging the engineered beam, that engineer will further specify the spread footing as seen fit.
 

                Comment:  Please note, dear reader, that in all instances, sub-slab-on-grade foundation elements are continuously separated at their top of face from the bottom of face of a slab-on-grade by a continuous bond break.

Home ] Up ] Foundat'n Plan Design ] Foundat'n Plan Close ] Foundat'n Plan Closer ] Anchor Bolts ] Concrete Design ] Concrete Joints ] Drainage Slopes ] Footing Drain ] [ Foundat'n Pad ] Foundat'n Speak ] Foundat'n Strip ] Gas Curb ] Grade Beam ] Slab Foundation ] Masonry Ledge ] Masonry Wythe ] Mod'd Grade Beam ] Pilasters ] Placement ] Radon Mitigation ] Rebar Reinforced ] Reinforced Corners ] Scored Concrete ] Slab-On-Ground ] Stone Water Table ]

 About Us jrp2h2000@yahoo.com 770-889-6964 Site MapPrivacy Policy

· · · · · · ·

(If this is your first visit to Before The Architect, please consider spending a few moments looking over the Site Map, in design of a custom home, plans, the home designers, about builders and building.  Before The Architect E-mail:  jrp2h2000@yahoo.com.)